Breaking federal laws

So today I put myself in a dangerous position. I was on the public bus when I read a sign saying “Federal law prohibits people from crossing the blue line when the bus is in motion”, and I was past the blue line. Once I noticed I quickly went behind it. Luckily, there were no federal agents on the bus (or if there were, they didn’t want to bust their cover) so I got away with a big one. My questions are 1: is this an actual federal law and 2: If I get busted, what can happen to me?

I’m pretty sure it said “Federal law prohibits operation of this bus if passengers are standing forward of the white line.” It’s not you who could be fined, but the bus owner.